Projectors using display devices (spatial optical modulators) such as liquid crystal display devices or DMDs (digital mirror devices) are capable of displaying images on a large screen, while they are compact and light in weight. In such projectors, an intense light from a light source is focused on a liquid crystal panel or DMD, modulated in accordance with an image signal, and enlarges and projects an image formed on the display device, thereby obtaining a high-quality large screen.
Also, increased brightness and improved quality year by year recently have allowed images on a large screen to be observed without dimming from extraneous light.
In the interior of such projectors, there are a large number of devices, such as lamps or light sources, liquid crystal panels, polarizers, and DMDs, that are required to be kept in a prescribed temperature range in order to offer the desired performance and to ensure reliability for long-term use. For example, because the display device is exposed to intense light and because the light source, a device power source, etc., generate a large amount of heat by themselves, the absence of appropriate cooling not only influences image quality but also causes thermal breakdown.
For this reason, projectors generally are equipped with an intake aperture and an exhaust aperture in a device housing, each port having a fan; and have a structure in which air is drawn into the interior of the projector through the intake aperture and then, after cooling each device, expelled out through the exhaust aperture.
However, dust is drawn in along with air from outside the device, and the attachment of such dust to the display device and to the periphery of the light source causes a reduction in brightness and color irregularities. For this reason, a sponge-like filter is disposed in the intake aperture for removing dirt or dust from taken-in air to obtain fresh air. In the case of a mainstream urethane filter, filter cleaning is required every several hundred hours.
In order to eliminate user inconveniences such as cleaning and exchange, a structure as disclosed in Patent Document 1 is desirable, for example. Patent Document 1 discloses a device having a function of automatically renewing an air filter that is mounted to electronic equipment for dust or oil filtration. Specifically, filtration is performed using a long filter roll by disposing a new part of the filter in the intake aperture. Under the control of this device, when contamination (clogging) of the filter is detected, a dirty part of the filter is taken-up automatically so that a new part of the filter is disposed over the entire intake aperture.
Patent Document 1: JP6-246120A